1. Field of the Invention
Containers for storing sets of interchangeable punches and dies for circular tabletting machines.
2. Description of the Prior Art
To better understand the nature of the present invention, a short description of the machine with which the containers of said invention is used is in order.
It is known in the art as a tabletting machine. It is circular and has many stations. Typically it may have as few as 18 stations and as many as 70. The machines are made by various manufacturers. They customarily include a circular table with a series of dies around the same near its periphery at regularly spaced intervals. There is a plate above the table and a plate below the table. The two plates have vertical through openings into which punches are adapted to be fitted for cooperation with the dies, there being an upper punch and a lower punch for each die. Customarily, there is a die for each station. Thus, if there are, for example, 48 stations, there will be 48 dies and 96 punches.
The table and the upper and lower plates rotate intermittently and in unison from station to station, stopping at each station where an operation may or may not be performed. Typical operations include feeding of a pharmaceutical powder, compacting of the powder into a tablet, ejection of the tablet, and cleaning of the punches and dies.
Many positions of the punches are intermediate positions, that is to say, positions at which the punches are intermediate an idle position and a fully operative position; or, phrased differently, they are either in an idle position or in a position in which they are moving toward a fully operative position. The punches customarily are caused to move by suitable cams that engage followers on the punches.
A complete set of dies for one size of tablet will be characterized by a uniform diameter of bore. However, all the tablets made with that die may not be the same. Some tablets may be heavier than others, depending upon the amount of powder fed into the die and the amount of compression exercised by the punches, i.e. the ultimate spacing between the punches. A machine may accept dies whose outer diameters are the same but whose bore diameters are different. Thus, there can be more than one set of dies which differ from one another by differing bore diameters. Different bore diameters will be used to make different sizes of tablets.
Similarly, the punches will be shaped to match different sizes of bore diameters. Thus, there will be one set of upper and lower punches sized to fit one bore diameter of dies, and another set of upper and lower punches sized to fit another set of bore diameters of dies, and there may be more than one set of upper and lower punches for a given bore diameter of dies if, for a given bore diameter, it is desired to make tablets of different weights (different heights).
All of these different sets of punches and dies can be used interchangeably in the same tabletting machine. More particularly, any given set of dies can be used in a given tabletting machine with a given set of upper and lower punches for the manufacture of a certain shape and weight of tablet. If it is desired to manufacture a different size and weight of tablet, a different set of dies and a different set of upper and lower punches will replace the set of dies and the set of upper and lower punches in the machine.
It thus will be apparent that any given tabletting machine will employ several sets of dies and correspondingly several sets of upper and lower punches. Only one set of dies and one set of upper and lower punches will be used on the tabletting machine at a time. The remaining sets of dies and the remaining sets of upper and lower punches must be stored, awaiting their turn for use. This has been the trade practice for many years.
There are, however, many problems associated with this trade practice. If the punches are so stored that their operative edges can touch metal, either during handling or while they are in storage, the operative surfaces can be nicked, scratched or dented, whereupon they must be re-ground in order to make perfect tablets. The same is true of the dies. Also, there is a tendency for the storage containers to occupy too great a space and, if one takes into account the large number of sets of dies and of upper and lower punches, a considerable problem is thus created. Therefore, it is important that the storage container hold the dies and punches in a highly compact arrangement which is particularly conservative as to the space they occupy.
At the present time, the most widely used type of storage box for punches constitutes a honeycomb of vertically elongated cells in which the punches are vertically arranged. With such a configuration, the punches tend to bang against the bottom of the storage box where ultimately they become scratched, nicked or dented and have to be redressed. There is no convenient storage space in these containers to accommodate the dies.